Focal plane array detectors are comprised of multiple sensors and, unlike single pixel detectors, they can capture a full-field image in a single shot. The charged coupled device (CCD) camera is a classic example of a focal place array operating in the optical and near infrared range. CCD cameras cannot operate in the terahertz range, however arrays of detectors such as microbolometers [1]}, [2]}, field-effect transistors (FETs) [3]} or carbon nanotubes [4]} can be used instead. Such arrays can operate up to video frame rates of around 50 Hz; however, their sensitivities are limited, and scaling to large pixel numbers can be challenging. Nonetheless, commercial systems based on uncooled microbolometers are available from companies such as INO [5]} and i2s [6]}. Despite significant progress in recent years, true real-time, full-field operation remains an unachieved goal for many terahertz imaging applications [7]}, therefore, novel atom-based terahertz imaging offers a viable alternative to the above-mentioned technologies as it provides the fastest frame rates currently possible. Table REF  summarises the pros and cons of various terahertz imaging systems. Thermal atomic vapours offer a good combination of properties i.e. very high speed, full-field imaging at room temperature but unlike TDS systems only operate at a single frequency.
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